Tag Archives: planck era

Sometime between 15 and 20 billion years ago the universe came into existence. Since the dawn of human awareness, we have grappled with the hows and whys of this event and out of this effort have sprung many ideas. An ancient Egyptian legend describes how the universe was created by Osiris Khepera out of a dark, boundless ocean called Nu and that Osiris Khepera created himself out of this ocean by uttering his own name. Human inventiveness has not stood still in the 5000 years since these ideas were popular. The modern theory of the Big Bang states that our universe evolved from an earlier phase billions of times hotter than the core of our sun and trillions of times denser than the nucleus of an atom. To describe in detail such extreme physical conditions, we must first have a firm understanding of the nature of matter and of the fundamental forces. At the high temperatures likely to have attended the Big Bang, all familiar forms of matter were reduced to their fundamental constituents. The forces of gravity and electromagnetism together with the strong and weak nuclear forces, were the essential means through which the fundamental particles of matter interacted.
The feedback between cosmology and particle physics is nowhere more clearly seen than in the study of the early history of the universe. In October, 1985 the giant accelerator at Fermilab acheived for the first time, the collision of protons and anti-protons at energies of 1.6 trillion electron volts, about 1600 times the rest mass of the proton. This was a unique event because for one split second, on a tiny planet in an undistinguished galaxy, a small window onto the Creation Event was opened for the first time in at least 15 billion years.

THE LIMITS OF CERTAINTY

The persuit by physicists of a single, all encompassing theory capable of describing the four natural forces has, as a by-product, resulted in some surprising glimpses of the Creation Event. Although such a theory remains perhaps several decades from completion, it is generally recognized that such a theory will describe physical conditions so extreme it is quite possible that we may never be able to explore them first- hand, even with the particle accelerators that are being designed today. For example, the Superconducting Supercollider to be built by the early 1990’s will cost 6 billion dollars and it will allow physicists to collide particles at energies of 40 trillion electron volts ( 40,000 GeV) matching the conditions prevailing 10 seconds after the Big Bang. The expected windfall from such an accelerator is enormous and will help to answer many nagging questions now plaguing the theoretical community, but can we afford to invest perhaps vastly larger sums of money to build machines capable of probing the quantum gravity world at 10 GeV? At these energies, the full unification of the natural forces is expected to become directly observable. How curious it is that definite answers to questions such as, ‘What was Creation like?’ and ‘Do electrons and quarks have internal structure?’ are so inextricably intertwined. Our ability to find answers to these two questions, among others, does not seem to be hampered by some metaphysical prohibition, but by the resources our civilization can afford to devote to finding the answers. Fortunatly, the situation is not quite so bleak, for you see, the ‘machine’ has already been ‘built’ and every possible experiment we can ever imagine has already been performed!

WHAT WE THINK WE KNOW

We are living inside the biggest particle accelerator ever created – the universe. Ten billion years before the sun was born, Nature’s experiment in high-energy physics was conducted and the experimental data can now be examined by studying the properties and contents of the universe itself. The collection of fundamental facts that characterize our universe is peculiar in that it derives from a variety of sources. A partial list of these ‘meta-facts’ looks like this:

1) We are here, therefore, some regions of the universe are hospitible to the creation of complex molecules and living, rational organisms.

2) Our Universe has 4 big dimensions and all are increasing in size as the universe expands in time and space.

3) There are 4 dissimilar forces acting in Nature.

4) Only matter dominates; no anti-matter galaxies exist and this matter is built out of 6 quarks and 6 types of leptons.

The task confronting the physicist and the astronomer is to create, hopefully, a single theory consistent with these metafacts that can then be used to derive the secondary characteristics of our universe such as the 2.7 K background radiation, the primordial element abundances, and galaxy formation. The interplay between the study of the macrocosm and the microcosm has now become so intense that astronomers have helped physicists set limits to the number of lepton families — No more than 4 are allowed otherwise the predicted cosmological abundance of helium would seriously disagree with what is observed. Physicists, on the other hand, use the astronomical upper limits to the current value of the cosmological constant to constrain their unification theories.

An extention to the standard Big Bang model called the Inflationary Universe (see The Decay of the False Vacuum) was created by MIT physicist Alan Guth in 1981. This theory combined Grand Unification Theory with cosmology and, if correct, allows astronomers to trace the history of the universe all the way back to 10 seconds after the Big Bang when the strong, weak and electromagnetic forces were unified into a single ‘electro-nuclear’ force. During the 4 years since the Inflationary Universe model was proposed, other theoretical developments have emerged that may help us probe events occurring at an even earlier stage, perhaps even beyond the Creation Event itself. Ten years ago, theoreticians discovered a new class of theories called Supersymmetric Grand Unified Theories ( SUSY GUTs). These theories, of which there are several competing types, have shown great promise in providing physicists with a unified framework for describing not just the electro-nuclear force but also gravity, in addition to the particles they act on (see The Planck Era: March 1984). Unfortunately, as SUSY GUTs were studied more carefully, it was soon discovered that even the most promising candidates for THE Unified Field Theory suffered from certain fundamantal deficiencies. For instance:

1) There were not enough basic fields predicted to accomodate the known particles.

2) Left and right-hand symmetry was mandated so that the weak force, which breaks this symmetry, had to be put in ‘by hand’.

3) Anomalies exist which include the violation of energy conservation and charge.

4) The Cosmological Constant is 10 times larger than present upper limits suggest.

In recent years, considerable effort has gone into extending and modifying the postulates of SUSY GUTs in order to avoid these problems. One avenue has been to question the legitimacy of a very basic premise of the field theories developed heretofore. The most active line of theoretical research in the last 25 years has involved the study of what are called ‘point symmetry groups’. For example, a hexagon rotated by 60 degrees about a point at its center is indistinguishable from one rotated by 120, 180, 240, 300 and 360 degrees. These 6 rotation operations form a mathematical group so that adding or subtracting any two operations always result in a rotation operation that is already a member of the group ( 180 = 120 + 60 etc). The Grand Unification Theories of the electro-nuclear interaction are based on point symmetry groups named SU(3), SU(2) and U(1) which represent analogous ‘rotations’ in a more complex mathematical space. In the context of ponderable matter, point symmetry groups are also the mathematical statement of what we believe to be the structure of the fundamental particles of matter, namely, that particles are point-like having no physical size at all. But what if this isn’t so? The best that experimental physics has to offer is that the electron which is one of a family of 6 known Leptons, behaves like a point particle at scales down to 10 cm, but that’s still an enormous distance compared to the gravitational Planck scale of 10 cm where complete unification with gravity is expected to occur.

By assuming that fundamental particles have internal structure, Michael Green at Queen Mary College and John Schwartz at Caltech made a remarkable series of discoveries which were anounced in the journal NATURE in April 1985. They proposed that, if a point particle were replaced by a vibrating ‘string’ moving through a 10-dimensional spacetime, many of the problems plaguing SUSY GUTs seemed to vanish miraculously. What’s more, of all the possible kinds of ‘Superstring’ theories, there were only two ( called SO(32) and E8 x E8′) that were: 1) Consistent with both the principles of relativity and quantum mechanics,2) Allowed for the asymmetry between left and right-handed processes and, 3) Were free of anomalies. Both versions were also found to have enough room in them for 496 different types of fields; enough to accomodate all of the known fundamental particles and then some! Superstring theories also have very few adjustable parameters and from them, certain quantum gravity calculations can be performed that give finite answers instead of infinite ones. In spite of their theoretical successes, Superstring theories suffer from the difficulty that the lightest Superstring particles will be completely massless while the next more massive generation will have masses of 10 GeV. It is not even clear how these supermassive string particles are related to the known particles which are virtually massless by comparison (a proton has a mass of 1 GeV!). It is also not known if the 496 different particles will cover the entire mass range between 0 and 10 GeV. It is possible that they may group themselves into two families with masses clustered around these two extreems. In the later instance, experimental physicists may literally run out of new particles to discover until accelerators powerful enough to create supermassive particles can be built.

An attractive feature of the SO(32) model, which represents particles as open-ended strings, is that gravity has to be included from the start in order to make the theory internally consistent and capable of yielding finite predictions. It is also a theory that reduces to ordinary point field theories at energies below 10 GeV. The complimentary theory, E8 x E8′, is the only other superstring theory that seems to work as well as SO(32) and treats particles as though they were closed strings without bare endpoints. This model is believed to show the greatest promise for describing real physical particles. It also includes gravity, but unlike SO(32), E8 x E8′ does seem to reduce at low energy, to the symmetry groups associated with the strong, weak and electromagnetic interactions, namely, SU(3), SU(2) and U(1).

If E8 x E8′ is destined to be the ‘ultimate, unified field theory’, there are some additional surprises in store for us. Each group, E8 and E8′, can be reduced mathematically to the products of the groups that represent the strong, weak and electromagnetic forces; SU(3) x SU(2) x U(1). If the E8 group corresponds to the known particles what does E8′ represent? In terms of its mathematical properties, symmetry considerations alone seem to require that the E8′ group should be a mirror image of E8. If E8 contains the groups SU(3), SU(2) and U(1) then E8′ contains SU(3)’, SU(2)’ and U(1)’. The primed fields in E8′ would have the same properties as those we ascribe to the strong, weak and electromagnetic forces. The E8′ particle fields may correspond to a completly different kind of matter, whose properties are as different from matter and anti-matter as ordinary matter is from anti-matter! ‘Shadow Matter’ as it has been called by Edward Kolb, David Seckel and Michael Turner at Fermilab, may actually co-exist with our own – possibly accounting for the missing mass necessary to close the universe. Shadow matter is only detectable by its gravitational influence and is totally invisible because the shadow world electromagnetic force (shadow light) does not interact with any of the particles in the normal world.

BEYOND SPACE AND TIME

The quest for a mathematical description of the physical world uniting the apparent differences between the known particles and forces, has led physicists to the remarkable conclusion that the universe inhabits not just the 4 dimensions of space and time, but a much larger arena whose dimensionality may be enormous (see Does Space Have More Than 3 Dimensions?). Both the Superstring theories and SUSY GUTs agree that our physical world has to have more than the 4 dimensions we are accustomed to thinking about. A remarkable feature of Superstring theory is that of all the possible dimensionalities for spacetime, only in 10-dimensions ( 9 space dimensions and 1 time dimension) will the theory lead to a computationally finite and internally consistent model for the physical world that includes the weak interaction from the outset, and where all of the troublesome anomalies cancil exactly. In such a 10-dimensional world, it is envisioned that 6 dimensions are now wrapped-up or ‘compactified’ into miniscule spheres that accompany the 4 coordinates of every point in spacetime. What would a description of the early universe look like from this new viewpoint? The 6 internal dimensions are believed to have a size of order 10 cm.

As we follow the history of the universe back in time, the 3 large dimensions of space rapidly shrink until eventually they become only 10 cm in extent. This happened during the Planck Era at a time, 10 seconds after the Creation Event. The appearance of the universe under these conditions is almost unimaginable. Today as we look out at the most distant quasar, we see them at distances of billions of lightyears. During the Planck Era, the matter comprising these distant systems was only 10 cm away from the material that makes-up your own body!

What was so special about this era that only 4 of the 10 dimensions were singled-out to grow to their enormous present size?. Why not 3 ( 2 space + 1 time) or 5 ( 4 space + 1 time)? Physicists have not as yet been able to develope an explanation for this fundamental mystery of our plenum, on the other hand, it may just be that had the dimensional breakdown of spacetime been other than ‘4 + 6’, the physical laws we are the products of, would have been totally inhospitable to life as we know it.

As we relentlessly follow the history of the universe to even earlier times, the universe seems to enter a progressively more and more symmetric state. The universe at 10 seconds after the Big Bang may have been populated by supermassive particles with masses of 10^15 GeV or about 10^-13 grams each. These particles ultimatly decayed into the familiar quarks and leptons once the universe had grown colder as it expanded. In addition, there may only have been a single kind of ‘superforce’ acting on these particles; a force whose character contained all of the individual attributes we now associate with gravity, electromagnetism and the strong and weak nuclear forces. Since the particles carrying the ‘superforce’ had masses similar to those of the supermassive particles co-existing then, the distinction between the force-carriers and the particles they act on probably broke-down completely and the world became fully supersymmetric.

To go beyond the Planck Era may require a radical alteration in our conventional way of thinking about time and space. Only glimpses of the appropriate way to think about this multidimensional landscape can be found in the equations and theories of modern-day physics. Beyond the Planck Era, all 10 dimensions (and perhaps others) become co-equal at least in terms of their physical size. The supermassive Superstring particles begin to take-on more of the characteristics of fluctuations in the geometry of spacetime than as distinguishable, ingredients in the primordial, cosmological ‘soup’. There was no single, unique geometry for spacetime but, instead, an ever-changing quantum interplay between spacetimes with an unlimited range in geometry. Like sound waves that combine with one another to produce interference and reinforcement, the spacetime that emerged from the Planck Era is thought to be the result of the superposition of an infin ite number of alternate spacetime geometries which, when added together, produced the spacetime that we are now a part of.

Was there light? Since the majority of the photons were probably not created in large numbers until at least the beginning of the Inflationary Epoc, 10^-36 seconds after the Big Bang, it is not unthinkable that during its earliest moments, the universe was born out of darkness rather than in a blinding flash of light. All that existed in this darkness before the advent of light, was an empty space out of which our 10-dimensional spacetime would later emerge. Of course, under these conditions it is unclear just how we should continue to think about time itself.

In terms of the theories available today, it may well be that the particular dimension we call Time had a definite zero point so that we can not even speak logically about what happened before time existed. The concept of ‘before’ is based on the presumption of time ordering. A traveler standing on the north pole can never move to a position on the earth that is 1 mile north of north! Nevertheless, out of ingrained habit, we speak of the time before the genesis of the universe when time didn’t exist and ask, “What happened before the Big Bang?”. The list of physicists investigating this ‘state’ has grown enormously over the last 15 years. The number of physicists, worldwide, that publish research on this topic is only slightly more than 200 out of a world population of 5 billion!

QUANTUM COSMOLOGY

In the early 1970’s Y. Zel’dovitch and A. Starobinski of the USSR along with Edward Tryon at Hunter College proposed that the universe emerged from a fluctuation in the vacuum. This vacuum fluctuation ‘ran away’ with itself, creating all the known particles out of empty space at the ‘instant’ of no-time. To understand what this means requires the application of a fundamental fact of relativistic quantum physics discovered during the latter half of the 1920’s. Vacuum fluctuations are a direct consequence of Heisenberg’s Uncertainty Principle which limits how well we can simultaneously know a particle’s momentum and location (or its total energy and lifetime). What we call empty space or the physical vacuum is a Newtonian fiction like absolute space and time. Rather than a barren stage on which matter plays-out its role, empty space is known to be filled with ‘virtual particles’ that spontaneously appear and disappear beyond the ability of any physical measurement to detect directly. From these ghost particles, a variety of very subtle phenomena can be predicted with amazing accuracy. Depending on the total rest mass energy of the virtual particles created in the vacuum fluctuation, they may live for a specific lifetime before Heisenberg’s Uncertainty Principle demands that they vanish back into the nothingness of the vacuum state. In such a quantum world, less massive virtual particles can live longer than more massive ones. Edward Tyron proposed that the universe is just a particularly long-lived vacuum fluctuation differing only in magnitude from those which occur imperceptably all around us. The reason the universe is so long lived in spite of its enormous mass is that the positive energy latent in all the matter in the universe is offset by the negative potential energy of the gravitational field of the universe. The total energy of the universe is, therefore, exactly zero and its maximum lifetime as a ‘quantum fluctuation’ could be enormous and even infinite! According to Tryon, “The Universe is simply one of those things which happens from time to time.”

This proposal by Tryon was regarded with some scepticism and even amusement by astronomers, and was not persued much further. This was a fate that had also befallen the work on 5-dimensional general relativity by Theodore Kaluza and Oskar Klein during the 1920’s which was only resurrected in the late 1970’s as a potent remedy for the ills plaguing supersymmetry theory.

In 1978, R. Brout, P. Englert, E. Gunzig and P. Spindel at the University of Brussels, proposed that the fluctuation that led to the creation of our universe started out in an empty, flat, 4-dimensional spacetime. The fluctuation in space began weakly, creating perhaps a single matter- antimatter pair of supermassive particles with masses of 10^19 GeV. The existence of this ‘first pair’ stimulated the creation from the vacuum of more particle-antiparticle pairs which stimulated the production of still others and so on. Space became highly curved and exploded, disgorging all of the superparticles which later decayed into the familiar leptons, quarks and photons.

Heinz Pagels and David Atkatz at Rockefeller University in 1981 proposed that the triggering agent behind the Creation Event was a tunneling phenomenon of the vacuum from a higher-energy state to a lower energy state. Unlike the Brout-Englert-Gunzig-Spindel model which started from a flat spacetime, Pagels and Atkatz took the complimentary approach that the original nothingness from which the universe emerged was a spatially closed, compact empty space, in other words, it had a geometry like the 2-D surface of a sphere. but the dimensionality of its surface was much higher than 2. Again this space contained no matter what-so-ever. The characteristics (as yet unknown) of the tunneling process determined, perhaps in a random way, how the dimensionality of spacetime would ‘crystallize’ into the 6+4 combination that represents the plenum of our universe.

Alex Vilenkin at Tufts University proposed in 1983 that our spacetime was created out of a ‘nothingness’ so complete that even its dimensionality was undefined. In 1984, Steven Hawkings at Cambridge and James Hartle at UCSB came to a similar conclusion through a series of quantum mechanical calculations. They described the geometric state of the universe in terms of a wavefunction which specified the probability for spacetime to have one of an infinite number of possible geometries. A major problem with the ordinary Big Bang theory was that the universe emerged from a state where space and time vanished and the density of the universe became infinite; a state called the Singularity. Hawkings and Hartle were able to show that this Big Bang singularity represented a specific kind of geometry which would become smeared-out in spacetime due to quantum indeterminacy. The universe seemed to emerge from a non-singular state of ‘nothingness’ similar to the undefined state proposed by Vilenkin. The physicist Frank Wilczyk expresses this remarkable situation the best by saying that, ” The reason that there is Something rather than Nothing is that Nothing is unstable.”

PERFECT SYMMETRY

Theories like those of SUSY GUTS and Superstrings seem to suggest that just a few moments after Creation, the laws of physics and the content of the world were in a highly symmetric state; one superforce and perhaps one kind of superparticle. The only thing breaking the perfect symmetry of this era was the definite direction and character of the dimension called Time. Before Creation, the primordial symmetry may have been so perfect that, as Vilenkin proposed, the dimensionality of space was itself undefined. To describe this state is a daunting challenge in semantics and mathematics because the mathematical act of specifying its dimensionality would have implied the selection of one possibility from all others and thereby breaking the perfect symmetry of this state. There were, presumably, no particles of matter or even photons of light then, because these particles were born from the vacuum fluctuations in the fabric of spacetime that attended the creation of the universe. In such a world, nothing happens because all ‘happenings’ take place within the reference frame of time and space. The presence of a single particle in this nothingness would have instantaneously broken the perfect symmetry of this era because there would then have been a favored point in space different from all others; the point occupied by the particle. This nothingness didn’t evolve either, because evolution is a time-ordered process. The introduction of time as a favored coordinate would have broken the symmetry too. It would seem that the ‘Trans-Creation’ state is beyond conventional description because any words we may choose to describe it are inherently laced with the conceptual baggage of time and space. Heinz Pagels reflects on this ‘earliest’ stage by saying, “The nothingness ‘before’ the creation of the universe is the most complete void we can imagine. No space, time or matter existed. It is a world without place, without duration or eternity…”

A perusal of the scientific literature during the last 20 years suggests that we may be rapidly approaching a major crossroad in physics. One road seems to be leading to a single unification theory that is so unique among all others that it is the only one consistent with all the major laws we know about. It is internally consistent; satisfies the principles of relativity and quantum mechanics and requires no outside information to describe the particles and forces it contains . A prototype of this may be superstring theory with its single adjustable parameter, namely, the string tension. The other road is much more bleak. It may also turn out that we will create several theoretical systems that seem to explain everything but have within them hard to detect flaws. These flaws may stand as barracades to further logical inquiry; to be uncovered only through experiments that may be beyond our technological reach. It is possible that we are seeing the beginning of this latter process even now, with the multiplicity of theories whose significant deviations only occur at energies near 10^19 GeV.

I find it very hard to resist the analogy between our current situation and that of the Grecian geometers. For 2000 years the basic postulates of Eulidean geometry and the consequences of this logical system, remained fixed. It became a closed book with only a few people in the world struggling to find exceptions to it such as refutations of the parallel line postulate. Finally during the 19th century, non-euclidean geometry was discovered and a renaissance in geometry occurred. Are physicists on the verge of a similar great age, finding themselves hamstrung by not being able to devise new ways of thinking about old problems? Egyptian cosmology was based on motifs that the people of that age could see in the world around them; water, sky, land, biological reproduction. Today we still use motifs that we find in Nature in order to explain the origin of the universe; the geometry of space, virtual particles and vacuum fluctuations. We can probably expect that in the centuries to follow, our descendents will find still other motifs and from them, fashion cosmologies that will satisfy the demands of that future age with, possibly, much greater accuracy and efficiency than ours do today. Perhaps, too, in those future ages, scientists will marvel at the ingenuity of modern physicists and astronomers, and how in the space of only 300 years, we had managed to create our own quaint theory as the Egyptians had before us.

In the meantime, physicists and astronomers do the best they can to fashion a cosmology that will satisfy the intellectual needs of our age. Today, as we contemplate the origin of the universe we find ourselves looking out over a dark, empty void not unlike the one that our Egyptian predecessors might have imagined. This void is a state of exquisite perfection and symmetry that seems to defy description in any linguistic terms we can imagine. Through our theories we launch mathematical voyages of exploration, and watch the void as it trembles with the quantum possibilities of universes unimaginable.

The Big Bang theory says that the entire universe was created in a tremendous explosion about 20 billion years ago. The enormity of this event is hard to grasp and it seems natural to ask ourselves ‘What was it like then?’ and ‘What happened before the Big Bang?’. To try to answer these queries, lets take a brief journey backwards in time.
We first see the formation of our own sun about 15 billion years after the Big Bang and then by 5 billion years, the formation of the first galaxies. By 700,000 years, the universe is awash with the fireball radiation that keeps all matter at a temperature of 4,000 degrees. Because of this, darkness is completely absent since every point in the sky glows with the brilliance of the sun. No stars, planets or even dust grains exist, just a hot dense plasma of electrons, protons and helium nuclei. By 3 minutes, we see helium form from the fusion of hydrogen atoms while the universe seeths at a temperature of nearly 1 billion degrees. The average density of matter is that of lead. By 1 second, the Lepton Era ends and the ratio of neutrons to protons has become fixed at 1 neutron for every 5 protons. The temperature is now 5 billion degrees everywhere. At about .0001 second, we watch as the Quark Era ends and the temperature of the fireball radiation rises to an incredable 1 trillion degrees. Quarks, for the first time, can combine in groups of two and three to become neutrons, protons and other types of heavy particles. The universe is now packed with matter as densly as the nucleus of an atom. A mountain like Mt. Everest could be squeezed into a volume no greater than the size of a golf ball!

By 1 billionth of a second, the temperature is 1 thousand trillion degrees and we see the electromagnetic and weak forces merge into one force. The density of the universe has increased to the point where the entire earth could be contained in a thimble. Quarks and anti-quarks are no longer confined inside of particles like neutrons and protons but are now part of a superheated plasma of unbound particles. As the remaining history of the universe unfolds, a long period seems to pass when nothing really new happens. Then, at a time 10(-35) second after the Big Bang, a spectac ular change in the size of the universe occurs. This is the GUT Era when the strong nuclear force becomes distinguishable from the weak and electromagnetic forces. The temperature is an incredable 10 thousand trillion trillion degrees and the density of matter has sored to nearly 10(75) gm/cm3. This number is so enormous that even our analogies are almost beyond comprehension. At these densities, the entire Milky Way galaxy could easily be stuffed into a volume no larger than a single hydrogen atom! Electrons and quarks together with their anti-particles, were the major constituents of matter and very massive particles called Leptoquark Bosons caused the quarks to decay into electrons and vice versa. If we now move forward in time we would witness the vacuum of space undergoing a ‘phase transition’ from a higher energy state to a lower energy state. This is analogous to a ball rolling down the side of a mountain and coming to rest in the lowest valley. As the universe ‘rolls down hill’ it begins a brief but stupendous period of expansion. The universe swells to billions of times its former size in almost no time at all.

In addition to this, a slight excess of matter over anti-matter appears becaus of the decay of massive particles called X Higgs Bosons. As we continue to watch the universe age, the remaining pairs of particles and anti-particles find themselves and vanish in a tremendous burst of annihilation. From this paroxysm, the bulk of the fireball radiation that we now observe is born.

The GUT Era is the last stop in our fanciful journey through time. If we had asked what it was like before the GUT Era, we would immediately have entered a vast no mans land where few indisputable facts would serve to gui de us. What does seem clear is that gravity is destined to grow in importance, eventually becoming the dominant force acting between parti cles, even at the microscopic level.

G R A V I T Y

According to theories developed since the 1930’s, what we call a ‘force’ is actually a collective phenomenon caused by the exchange of innumerable, force-carrying particles called gauge bosons. The electromagnetic force, which causes like charges to attract and dissimilar ones to repel, is transmitted by gauge bosons called photons, the strong force that binds nucleii together is transmitted by gluons and the weak force which causes particles to decay is transmitted by the, recently discovered, W and Z Intermediate Vector Bosons. In an analogous way, physicists believe that gravity is transmitted by particles called Gravitons. If gravity really does have such a quantum property, its effects should appear once quarks and electrons can be forced to within 10(-33) centimeter of one another, a distance called the Planck length. To acheive these conditions, quarks and electrons will have to be collided at energies of 10(19) GeV. An accelerator patterned after the 2-mile, Stanford Linear Accelerator would have to be 1 light-year in length to push particles to these incredable energies! Fortunatly, what humans find impossible to do, Nature with its infinite resources finds less difficult. Before the universe was 10(-43) second old, matter routinely experienced collisions at these energies. This period is what we call the Planck Era.

THROUGH A LOOKING GLASS, DARKLEY

Since our technology will not allow us to physically reproduce the conditions during these ancient times, we must use our mathematical theories of how matter behaves to mentally explore what the universe was like then. We know that the appearence of the universe before 10(-43) second can only be adequatly described by modifying the Big Bang theory because this theory is, in turn, based on the General Theory of Relativity. General Relativity tells us how gravity operates on the macroscopic scale of planets, stars and galaxies. At the Planck scale, we need to extend General Relativity so that it includes not only the macroscopic properties of gravity but also is microscopic characteristics as well. The theory of ‘Quantum Gravity’ is still far from completion but physicists tend to agree that, at the very least, Quantum Gravity must combine the conceptual elements of the two great theories of modern physics: General Relativity and Quantum Mechanics.

In the language of General Relativity, gravity is a consequence of the deformati on of space caused by the presence of matter and energy. Gravity is just another name for the amount of curvature in the geometry of 3-dimensional space. In Quantum Gravity theory, gravity is produced by massless gravitons so that gravitons now represent individual packages of curved space that travel through space at the speed of light.

The appearence and dissappearence of innumerable gravitons gives the geometry of space a very lumpy and dynamic appearance. John Wheeler at Princeton University thinks of this as a foamy, sub-structure to space where the geometry of space twists and contorts so that far flung regions of space may suddenly find themselves connected by ‘wormholes’ which constantly appear and dissappear within 10(-43) seconds. Even as you are reading this article, this frenetic activity is occurring in the hyper-microscopic domain, 100 billion billion times smaller than the nucleus of an atom. For a comparison, the size of the sun and the size of a single atom stand in about this same proportion. Although Quantum Gravity effects are completely undetectable today at the atomic and nuclear scale, during the Planck Era, macroscopic and microscopic worlds merged and the Quantum Gravity of the microcosm suddenly became the Quantum Cosmology of the macrocosm!

QUANTUM COSMOLOGY

As we approach the end of the Planck Era, the random appearance and dissappearance of innumerable gravitons will eventually force us to give up the concept of a specific geometry to 3-dimensional space. Instead, the geometry at a given moment will have to be thought of as an average over all 3-dimensional space geometries that are possible. Once again, the reason for this is that particles are squeezed so closely together that we can now see individual gravitons moving around in the space between them causing space to become curved. We can no longer get away with saying that the space between two quarks, for example, is flat. This is what we mean when we say that the gravitational force between them is insignificant when compared to the other three forces of Nature.

To make matters much worse, not only will Quantum Gravity not allow us to calculate the exact 3-dimensional geometry to space but, at the Planck scale, it will not allow us to simultaneously determine its exact geometry and precise rate of change in time. What this means is that we may never be able to calculate with any certainty exactly what the history of the universe was like before 10-43 second. Today, the large-scale geometry of space is one of three possible types: flat and infinite, negatively curved and infinite or positively curved and finite. During the Planck Era, the ‘large-scale’ geometry was contorted by wormholes and and infinite number of possibilities were possible. To probe the history of the universe then would be like trying to trace your ancestral roots if every human being on earth had a possibility of being one of your parents. Now try to trace your family tree back a few generations! The farther back in time you go, the greater are the number of possible ancestors you could have had. An entirely new conception of what we mea n by ‘a history for the universe’ will have to be developed. Even the concepts of space and time will have to be completely re-evaluated in the face of the qua ntum fluctuations of spacetime at the Planck Era!

THE BIRTH OF THE UNIVERSE

The picture that seems to emerge from using our sketchy outline of what Quantum Gravity theory might look like is that as we approach the Planck Era, gravitons are exchanged between quarks and electrons with increasingly higher energy and in greater number. By the time we reach the end of the Planck Era at 10(-43) second, gravitons will begin to carry as much energy as the other force carriers (Gluons, IVBs and Photons). At still earlier times, a period of complet e symmetry and unification between all the natural forces will ensue. Only one super-unified force exists here (gravity) and only one kind of particle dominates the activity of this age(Gravitons).

During the early 70’s, the Russian physicists Ya. Zel’dovitch and A. Starobinski of the USSR Academy of Science proposed that the rapidly changing geometry of space during the Planck Era may actually have created all the matter, anti-matter and radiation that existed soon after Creation. In their picture of Creation, the rapidly changing geometry of space created particles and anti-particles with masses of 10(19) GeV. This production of matter and anti-matter removed energy from the enormous fluctuations occuring in the geometry of space and eventually succeeded in damping them out altogether by the end of the Planck Era. They also found that the rate of particle creation increased as more and more particles were created.

Several recent studies by Physicists Edward Tryon of Hunter College, R. Brout, F. Englert and E. Gunzig of the University of Brussels and david Atkatz and Heinz Pagels of the Rockefeller University have shed additional light on what Creation may have been like. Imagine if you can, nothing at all! This is the primordial vacuum of space. There is complete darkness here, no light yet exists. The number of dimensions to space was probably not the normal 3 that we are so accustomed to but may have been as high as 11 according to Supergravity theory! In this infinite emptiness, random fluctuations occurred that ever so slightly changed the energy of the vacuum at various points in space. Eventually, one of these fluctuations attained a critical energy and began to grow. As it grew, very massive particles called leptoquarks and anti-leptoquarks were created, causing the expansion to accelerate. This is much like a ball rolling down a hill that moves slowly at first and then gains momentum. The expansion of the proto-universe, in turn, caused still more leptoquarks to be created. This furious cycle continued until, at long last, the leptoquarks decayed into quarks, leptons (electrons, muons etc) and their anti-particles and the universe emerged from the Planck Era. Particle creation stopped once the fluctuations in the geometry of space subsided.

So, we are left with the remarkable possibility that, in the beginning, there ex isted quite literally, nothing at all and from it emerged nearly all of the matter and radiation that we now see. This process has been described by the physicist Frank Wilczyk at the University of California, Santa Barbara by saying, ” The reason that there is something instead of nothing is that nothing is unstable”. A ball sitting on the summit of a steep hill needs but the slightest tap to set it in motion. A random fluctuation in space was apparently all that was required to unleash the incredable latent energy of the vacuum, thus creating matter and energy and an expanding universe from ‘nothing at all’.

The universe did not spring into being instantaneously but was created a little bit at a time in a ‘bootstrap’ process. Once a few particles were created by quantum fluctuations of the empty vacuum, it became easier for a few more to appear and so, in a rapidly escalating process, the universe gushed forth from nothingness.

How long did this take? The primordial vacuum could have existed for an eternity before the particular fluctuation that gave rise to our universe happened. Physicist Edward Tryon expresses this best by saying that ” Our universe is simply one of those things that happens from time to time”.

The principles of Quantum Gravity may ultimatly force us to reconsider questions like ‘What happened before the Big Bang?’ because they imply the existence of something (time) that may not have any meaning at all. These questions may be as empty of meaning as an explorer on the north pole asking, ‘Which way is North?’. Only the complete theory of Quantum Gravity may tell us how to ask the right questions!

The Big Bang theory says that the entire universe was created in a tremendous explosion about 14 billion years ago. The enormity of this event is hard to grasp and it seems natural to ask ourselves ‘What was it like then?’ and ‘What happened before the Big Bang?’.

Thanks to what physicists call the Standard Model, we have a detailed understanding of quantum physics, matter, energy and force that let us reproduce what the universe looked like as early as a billionth of a second after the Big Bang. The results of high-precision observational cosmology also let us verify that the Standard Model predictions match what we see as the general properties of the matter and energy in our universe up until this unimaginable time. We can actually go a bit farther back towards the beginning thanks to detailed studies of the cosmic background radiation!

At a time 10(-36) second ( that is a trillionth of a trillionth of a trillionth of a second!) after the Big Bang, a spectacular change in the size of the universe occurs. This is the Inflationary Era when the strong nuclear force becomes distinguishable from the weak and electromagnetic forces. The temperature is an incredable 10 thousand trillion trillion degrees and the density of matter has sored to nearly 10(75) gm/cm3. This number is so enormous even our analogies are almost beyond comprehension. At these densities, the entire Milky Way galaxy could easily be stuffed into a volume no larger than a single hydrogen atom!

Between a billionth of a second and 10(-35) seconds is a No Man’s Land currently in accessible to our technology and requires instruments such as the CERN Large Hadron Collider scaled up to the size of our solar system or even larger! This is also the domain of the so-called Particle Desert that I previously wrote about, and the landscape of the predictions made by supersymmetric string theory, for which there is as yet no evidence of their correctness despite decades of intense theoretical research.

THROUGH A LOOKING GLASS, DARKLEY

Since our technology will not allow us to physically reproduce the conditions during these ancient times, we must use our mathematical theories of how matter behaves to mentally explore what the universe was like then. We know that the appearence of the universe before 10(-43) second can only be adequatly described by modifying the Big Bang theory because this theory is, in turn, based on the General Theory of Relativity. At the Planck Scale, we need to extend General Relativity so that it includes not only the macroscopic properties of gravity but also is microscopic characteristics as well. The theory of ‘Quantum Gravity’ is still far from completion but physicists tend to agree that there are some important quide-posts to help us understand how it applies to Big Bang theory.

QUANTUM COSMOLOGY

In the language of General Relativity, gravity is a consequence of the deformati on of space caused by the presence of matter and energy. In Quantum Gravity theory, gravity is produced by massless gravitons, or strings (in what is called string theory), or loops of energy (in what is called loop quantum gravity), so that gravitons now represent individual packages of curved space.

The appearence and dissappearence of innumerable gravitons gives the geometry of space a very lumpy and dynamic appearance. The geometry of space twists and contorts so that far flung regions of space may suddenly find themselves connected by ‘wormholes’ and quantum black holes, which constantly appear and dissappear within 10(-43) seconds. The geometry of space at a given moment will have to be thought of as an average over all 3-dimensional space geometries that are possible.

What this means is that we may never be able to calculate with any certainty exactly what the history of the universe was like before 10(-43) seconds. To probe the history of the universe then would be like trying to trace your ancestral roots if every human being on earth had a possibility of being one of your parents. Now try to trace your family tree back a few generations! An entirely new conception of what we mean by ‘a history for the universe’ will have to be developed. Even the concepts of space and time will have to be completely re-evaluated in the face of the quantum fluctuations of spacetime at the Planck Era!

Now we get to a major problem in investigating the Planck Era.

BUT WAIT…THERE’S MORE!

Typically we make observations in nuclear physics by colliding particles and studying the information created in the collision, such as the kinds of particles created, their energy, momentum, spin and other ‘quantum numbers’. The whole process of testing our theories relies on studying the information generated in these collisions, searching for patterns, and comparing them to the predictions. The problem is that this investigative process breaks down as we explore the Planck Era. When the quantum particles of space (gravitons, strings or loops)collide at these enormous energies and small scales, they create quantum black holes that immediately evaporate. You cannot probe even smaller scales of space and time because all you do is to create more quantum black holes and wormholes. Because the black holes evaporate into a randomized hailstorm of new gravitons you cannot actually make observations of what is going on to search for non-random patterns the way you do in normal collisions!

Quantum Gravity, if it actually exists as a theory, tells us that we have finally reached a theoretical limit to how much information we can glean about the Planck Era. Our only viable options involve exploring the Inflationary Era and how this process left its fingerprints on the cosmic background radiation through the influence of gravitational waves.

Fortunately, we now know that gravity waves exist thanks to the discoveries by the LIGO instrument in 2016. We also have indications of what cosmologists call the cosmological B-Modes which are the fingerprints of primordial gravity waves interacting with the cosmic background radiation during the Inflationary Era.

We may not be able to ever study the Planck Era conditions directly when the universe was only 10(-43) seconds old, but then again, knowing what the universe was doing 10(-35) seconds after the Big Bang all the way up to the present time is certainly an impressive human intellectual and technological success!